dyoo/whalesong — pull request #103 by soegaard (2014-06-29 22:28:05+00:00)
Title: Behaviour of (letrec ([x x]) x) changed in Racket

The latest Racket has changed the behaviour of (letrec ([x x]) x).
Currently any program beginning with #lang whalesong fails due
to an "x undefined" error. The undefined value is now exported
from racket/undefined.